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Principle 1 – Perceivable

Information and user interface components must be presentable to users in ways they can perceive.

Guideline 1.1 – Text Alternatives

Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.

Sufficient Advisory Failures

Advisory Techniques

Providing sign language videos for audio-only files (future link)

1.1.1Non-text Content

Level A

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below.

Controls, Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to Guideline 4.1 for additional requirements for controls and content that accepts user input.)

Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2 for additional requirements for media.)

Test: If non-text content is a test or exercise that would be invalid if presented in text, then text alternatives at least provide descriptive identification of the non-text content.

Sensory: If non-text content is primarily intended to create a specific sensory experience, then text alternatives at least provide descriptive identification of the non-text content.

CAPTCHA: If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.

Decoration, Formatting, Invisible: If non-text content is pure decoration, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.

Situation D: If non-text content is time-based media (including live video-only and live audio-only); a test or exercise that would be invalid if presented in text; or primarily intended to create a specific sensory experience:

Providing a descriptive label (future link) using one of the following techniques:

Advisory Techniques for Success Criterion 1.1.1

General Techniques for Informative Non-Text Content (Advisory)

Identifying informative non-text content (future link)

Keeping short descriptions short (future link)

Describing images that include text (future link)

Providing a longer description of the non-text content where only a descriptive label is required using a technology-specific technique (for an accessibility-supported content technology) for long description listed above (future link)

Providing different sizes for non-text content when it cannot have an equivalent accessible alternative (future link)

Using server-side scripts to resize images of text (future link)

General Techniques for Live Non-Text Content (Advisory)

Linking to textual information that provides comparable information (e.g., for a traffic Webcam, a municipality could provide a link to the text traffic report.) (future link)

General techniques to minimize the barrier of CAPTCHAs

Providing more than two modalities of CAPTCHAs (future link)

Providing access to a human customer service representative who can bypass CAPTCHA (future link)

1.2.3Audio Description or Media Alternative (Prerecorded)

Level A

An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such.

1.2.7Extended Audio Description (Prerecorded)

Level AAA

Where pauses in foreground audio are insufficient to allow audio descriptions to convey the sense of the video, extended audio description is provided for all prerecorded video content in synchronized media.

Situation B: The technology in use does NOT provide the semantic structure to make the information and relationships conveyed through presentation programmatically determinable:

Making information and relationships conveyed through presentation programmatically determinable or available in text using the following techniques: (future link) using one of the following techniques:

1.4.1Use of Color

Level A

Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

Note 1: This success criterion addresses color perception specifically. Other forms of perception are covered in Guideline 1.3 including programmatic access to color and other visual presentation coding.

1.4.2Audio Control

Level A

If any audio on a Web page plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume independently from the overall system volume level.

Note 1: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether or not it is used to meet other success criteria) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

1.4.3Contrast (Minimum)

The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following:

Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;

Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.

Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

1.4.6Contrast (Enhanced)

The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following:

Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 4.5:1;

Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.

Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

1.4.7Low or No Background Audio

Level AAA

For prerecorded audio-only content that (1) contains primarily speech in the foreground, (2) is not an audio CAPTCHA or audio logo, and (3) is not vocalization intended to be primarily musical expression such as singing or rapping, at least one of the following is true:

No Background: The audio does not contain background sounds.

Turn Off: The background sounds can be turned off.

20 dB: The background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sounds that last for only one or two seconds.

Fourth Requirement: Techniques to ensure line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing

Fifth Requirement: Techniques to ensure text can be resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text on a full-screen window

Not interfering with the user agent's reflow of text as the viewing window is narrowed (future link) OR

G146: Using liquid layout AND using measurements that are relative to other measurements in the content by using one of the following techniques:

Principle 2 – Operable

User interface components and navigation must be operable.

Guideline 2.1 – Keyboard Accessible

Make all functionality available from a keyboard.

2.1.1Keyboard

Level A

All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints.

Note 1: This exception relates to the underlying function, not the input technique. For example, if using handwriting to enter text, the input technique (handwriting) requires path-dependent input but the underlying function (text input) does not.

Note 2: This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation.

2.1.2No Keyboard Trap

Level A

If keyboard focus can be moved to a component of the page using a keyboard interface, then focus can be moved away from that component using only a keyboard interface, and, if it requires more than unmodified arrow or tab keys or other standard exit methods, the user is advised of the method for moving focus away.

Note 1: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

Sufficient Techniques for Success Criterion 2.1.3

No additional techniques exist for this Success Criterion. Follow techniques for Success Criterion 2.1.1. If that is not possible because there is a requirement for path-dependent input, then it is not possible to meet this Level AAA Success Criterion.

Failures for Success Criterion 2.1.3

Guideline 2.2 – Enough Time

2.2.1Timing Adjustable

For each time limit that is set by the content, at least one of the following is true:

Turn off: The user is allowed to turn off the time limit before encountering it; or

Adjust: The user is allowed to adjust the time limit before encountering it over a wide range that is at least ten times the length of the default setting; or

Extend: The user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action (for example, "press the space bar"), and the user is allowed to extend the time limit at least ten times; or

Real-time Exception: The time limit is a required part of a real-time event (for example, an auction), and no alternative to the time limit is possible; or

Essential Exception: The time limit is essential and extending it would invalidate the activity; or

20 Hour Exception: The time limit is longer than 20 hours.

Note 1: This success criterion helps ensure that users can complete tasks without unexpected changes in content or context that are a result of a time limit. This success criterion should be considered in conjunction with Success Criterion 3.2.1, which puts limits on changes of content or context as a result of user action.

2.2.2Pause, Stop, Hide

Level A

For moving, blinking, scrolling, or auto-updating information, all of the following are true:

Moving, blinking, scrolling: For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than five seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it unless the movement, blinking, or scrolling is part of an activity where it is essential; and

Auto-updating: For any auto-updating information that (1) starts automatically and (2) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it or to control the frequency of the update unless the auto-updating is part of an activity where it is essential.

Note 2: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

Note 3: Content that is updated periodically by software or that is streamed to the user agent is not required to preserve or present information that is generated or received between the initiation of the pause and resuming presentation, as this may not be technically possible, and in many situations could be misleading to do so.

Note 4: An animation that occurs as part of a preload phase or similar situation can be considered essential if interaction cannot occur during that phase for all users and if not indicating progress could confuse users or cause them to think that content was frozen or broken.

Guideline 2.3 – Seizures

Advisory Techniques

2.3.1Three Flashes or Below Threshold

Level A

Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds.

Note 1: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

2.4.4Link Purpose (In Context)

Level A

The purpose of each link can be determined from the link text alone or from the link text together with its programmatically determined link context, except where the purpose of the link would be ambiguous to users in general.

Advisory Techniques for Success Criterion 3.1.1

3.1.2Language of Parts

Level AA

The human language of each passage or phrase in the content can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text.

3.1.5Reading Level

Level AAA

When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplemental content, or a version that does not require reading ability more advanced than the lower secondary education level, is available.

Note: Different sites may address this Success Criterion in different ways. An audio version of the content may be helpful to some users. For some people who are deaf, a sign language version of the page may be easier to understand than a written language version since sign language may be their first language. Some sites may decide to do both or other combinations. No technique will help all users who have difficulty. So different techniques are provided as sufficient techniques here for authors trying to make their sites more accessible. Any numbered technique or combination above can be used by a particular site and it is considered sufficient by the Working Group.

Advisory Techniques for Success Criterion 3.1.5

Providing text for navigational and landing pages that requires reading ability that is less advanced than the lower secondary education level (future link)

Making metadata viewable by humans (future link) using one of the following techniques:

EXAMPLE: Providing, in metadata, URI(s) that point to a pre-primary-reading-level and a primary-reading-level text transcript of a new scientific discovery advanced-reading-level article. (future link)

Providing progressive complexity for site and page content (future link)

Note 1: Text alternatives that are “consistent” are not always “identical.” For instance, you may have an graphical arrow at the bottom of a Web page that links to the next Web page. The text alternative may say “Go to page 4.” Naturally, it would not be appropriate to repeat this exact text alternative on the next Web page. It would be more appropriate to say “Go to page 5”. Although these text alternatives would not be identical, they would be consistent, and therefore would satisfy this Success Criterion.

Note 2: A single non-text-content-item may be used to serve different functions. In such cases, different text alternatives are necessary and should be used. Examples can be commonly found with the use of icons such as check marks, cross marks, and traffic signs. Their functions can be different depending on the context of the Web page. A check mark icon may function as “approved”, “completed”, or “included”, to name a few, depending on the situation. Using “check mark” as text alternative across all Web pages does not help users understand the function of the icon. Different text alternatives can be used when the same non-text content serves multiple functions.

Advisory Techniques for Success Criterion 3.2.4

Ensuring that the text alternative conveys the function of the component and what will happen when the user activates it (future link)

Using the same non-text content for a given function whenever possible (future link)

Note: The techniques at the end of the above list should be considered “last resort” and only used when the other techniques cannot be applied to the page. The earlier techniques are preferred because they increase accessibility to a wider user group.

Techniques for providing suggestions to the user (Advisory)

Providing a text description that contains information about the number of input errors, suggestions for corrections to each item, and instructions on how to proceed (future link)

Providing a text description that contains suggestions for correction as the first item (or one of the first items) of content, or emphasizing this information in the content (future link)

Displaying errors and suggestions in the context of the original form (for example, re-displaying a form where input errors and suggestions for correction are highlighted and displayed in the context of the original form) (future link)

3.3.4Error Prevention (Legal, Financial, Data)

Level AA

For Web pages that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true:

Reversible: Submissions are reversible.

Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.

Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.

Principle 4 – Robust

Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.

Guideline 4.1 – Compatible

Maximize compatibility with current and future user agents, including assistive technologies.

Sufficient Advisory Failures

Advisory Techniques

Avoiding deprecated features of W3C technologies (future link)

Not displaying content that relies on technologies that are not accessibility-supported when the technology is turned off or not supported. (future link)

4.1.1Parsing

Level A

In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.

Note 1: Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quotation mark are not complete.

Failures for Success Criterion 4.1.1

4.1.2Name, Role, Value

Level A

For all user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically set; and notification of changes to these items is available to user agents, including assistive technologies.

Note 1: This success criterion is primarily for Web authors who develop or script their own user interface components. For example, standard HTML controls already meet this success criterion when used according to specification.

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Document Information

Status: Updated 20 Jul 2017. Version 2.5. Lead Developer: Eric Eggert (W3C). Project Lead: Shadi Abou-Zahra (W3C).Previous editors and developers: Gregg Vanderheiden, Loretta Guarino Reid, Ben Caldwell, Shawn Lawton Henry, Gez Lemon.The 2017 redesign was developed by the Education and Outreach Working Group (EOWG) and the Web Content Accessibility Guidelines Working Group (WCAG WG), with support from the WAI-DEV project, a project of the European Commission IST Programme.